I have a DSL 100h that has been fading in and out and crackling for quite some time. It seems to only happen on the clean channel and makes no difference, if I have my pedal board plugged in or not. I have the fx loop turned off, so I believe that that part of the circuit is out of the equation. I just swapped out the tubes because I suspected the pre amp tubes were bad from some other things I read and still no luck. Has anyone else experienced this?